APM Hexseal developed and patented the first self-sealing screw over 50 years ago. Since then, APM has enhanced the design for better performance and versatility. The APM o-ring Seelskrew© system, does not require special training or screw handling techniques. The proprietary asymmetrical groove is cold formed under the head of the screw and provides a place for the o-ring to compress, resulting in 360° contact with the mating surface. The screw is delivered with the o-ring installed on the screw, and can be re-used a number of times, making equipment servicing easy.